Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

449
FXUS63 KLOT 101939
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
139 PM CST Sat Jan 10 2026

.KEY MESSAGES...

- Increasing signal for quick snow accumulations this evening
  with embedded robust wind-whipped snow showers/squalls leading
  to localized quick snow accumulations and rapidly-varying
  conditions. Hazardous travel conditions expected within
  heavier snow.

- Up and then down temperatures are expected next week with
  occasional opportunities for (mainly light) precipitation.

&&

.DISCUSSION...
Issued at 139 PM CST Sat Jan 10 2026

Through Sunday:

Main focus in the short term remains on the incoming stout
shortwave and attendant vort max currently slicing across
southern Iowa. Based on the latest guidance along with
eyeballing recent IR/WV satellite trends, it looks like the main
area of maximized DCVA will focus roughly south of a La Salle
to Rensselaer line this evening. Guidance suggests a secondary
maxima potentially focusing near the I-88 corridor. Both of
these may lead to corridors of enhanced, wind- whipped snow
showers to even bonafide squalls this evening.

Along and south of the southern corridor (La Salle - Rensselaer
line):

More coherent/organized low-level f-gen will coincide with
steepening low-level lapse rates and near-surface CAPE. The RAP
has remained incredibly consistent since earlier this morning
depicting a lobe of locally maximized ascent tracking within
this corridor between about 5-6 PM and 9-10 PM (earlier west,
later east) with peak UVVs pushing 30+ ubar/second through a
deepening DGZ which is exceptionally intense. It`s always
difficult getting super detailed with these small-scale features
even at this short of a time range, but based on the latest
radar trends, feeling more confident that at least the northern
terminus of this enhanced ascent will poke into our southern
locales this evening.

Given all of this, along with the still stratiform nature to
incoming precipitation, have boosted PoPs and snow amounts in
this region this evening. Wherever this feature tracks, snow
totals will likely overperform what`s in the gridded forecast in
a hyper-localized area (perhaps a 10-mile wide area or less),
and it would not be surprising to see a few 3-4" amounts with
the forcing profile supportive of very large dendrites. It`s
possible this axis ends up just south of our area, but it`s too
close to slice that thin at this point. The one slight detractor
here is that air temperatures are currently in the upper 30s,
and will only fall and then wetbulb to around freezing as this
activity pushes through, but if rates become heavy, the large
snowflake size would likely result in quick roadway
accumulations. Will highlight this threat area with a Special
Weather Statement, and if trends continue to deteriorate, a
short-fused Winter Weather Advisory may be warranted (it`s
possible snowfall continues a bit longer than a snow squall
warning is meant to handle and, while winds will become gusty,
may not reach the level of a true snow squall).

Near the I-88 corridor:

Farther to the north, another area of locally enhanced DCVA is
forecast to coincide with at least ephemeral low-level f-gen in
the vicinity of the I-88 corridor. While modeled instability
and lapse rates are higher compared to farther south, the
remaining parameters are not as well tied together/coherent.
That said, recent HRRR, HRDPS, and RAP runs have somewhat
consistently shown a signal for localized streets of enhanced
QPF in this area. Have also increased PoPs and snow amounts a
bit. Main timing for this activity is also about 5 PM to 1 AM.
Much like summertime convection, many locations will likely
receive little or no snow with this activity, while nearby
locales may pick up a quick inch or so.

Flurries and snow showers will likely persist after midnight
tonight. A secondary vort lobe will push through the area
towards midnight which will serve as another focus for more
concentrated snow shower activity. The last push of light snow
showers arrives towards daybreak, and activity should begin to
diminish through the rest of Sunday morning. Lake effect snow
showers will likely persist in the vicinity of Porter County
towards midday with some localized higher accumulations there
before activity winds down towards midday/early afternoon.
Guidance suggests that a thin stratus layer may re-develop (or
perhaps never fully erode) on Sunday and have increased sky
cover a bit to cover this.

Carlaw


Sunday Night through Saturday:

Anomalously strong mid-upper ridging will establish near the
Pacific Coast through next week, resulting in a predominantly
northwesterly flow pattern across much of the northern CONUS.
Seasonable conditions on Sunday evening will give way to a few
days of solidly above normal temps (through Tuesday evening),
followed by a return to more seasonable readings for mid-January
through the rest of the week. There will be occasional
opportunities for precipitation, though the deep northwest flow
pattern will be unfavorable for any moisture-laden systems.

Following an evening dip in temps to below 30F Sunday evening,
strong ~1035 mb surface high pressure will settle into the Mid-
South. In response, as a fairly robust low-level jet shifts
overhead, a commensurate increase in southwest winds will result
in rising temperatures overnight into early Monday.

With the first in a series of clipper-type systems passing well
to the north Monday into Tuesday, the breezy warm advection
regime will result in highs in the lower to mid 40s Monday, near
to a bit above freezing lows Monday night, and then highs into
the mid-upper 40s to around 50F on Tuesday. Some spotty light
rain showers or just sprinkles will be possible on Tuesday into
the early evening as the next clipper wave reaches the area. The
cold front trailing from an associated surface low pressure
center passing through or just north of the northern Great Lakes
will then shift across the area by the evening, bringing the
early workweek stretch of mild temps to an end.

Mid-upper troughing will deepen over the eastern US on
Wednesday as a few embedded short-wave impulses press
southeastward. The cold advection regime on Wednesday should
support at least scattered snow showers (30-50% PoPs still look
reasonable for now), though marginal surface temps to start the
day and the showery nature of the snow should tend to limit
accumulation/impact potential. With the most robust mid-level
height falls confined to the morning through midday, snow shower
coverage and/or intensity may tend to diminish into the
afternoon.

We`ll then need to watch for a window of favorable lake effect
thermodynamics Wednesday night into pre-dawn Thursday (if
forecast mid-level subsidence is not too deleterious),
supporting ~30-40% chance PoPs for portions of northeast IL and
northwest IN. Any break following the possible lake effect snow
showers will likely be short-lived, with signs pointing toward
an additional clipper system or two affecting the region
sometime in the Thursday PM-Saturday timeframe. Some guidance
members suggest the clipper short-wave could temporarily become
a cut-off low into the start of the weekend. If this comes to
pass, warm advection driven snow late Thursday PM-Thursday night
would be followed by on-and-off snow showers Friday into
Saturday.

Castro/Ogorek

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1155 AM CST Sat Jan 10 2026

Ongoing SN mixed with RA at the Chicago metro sites will end
within the next hour or so. MVFR ceilings will also begin to
scatter throughout the afternoon. Meanwhile, expect WNW winds
to gust up to 25 knots through sunset.

A pair of compact mid-level waves, one over central Iowa and
another over central Minnesota, will cross the northern half of
Illinois in succession this evening as modest cold-air advection
steepens low-level lapse rates. Isolated to scattered gusty
SHSN are expected across the area throughout the evening. While
the strongest SHSN will be widely isolated and may not affect
every terminal this evening, they will contain wind gusts to
around 30 knots and LIFR visibility. Have included TEMPO IFR
visibility as most SHSN should remain in that range, but there
is a distinct scenario where conditions vary between P6SM with
FEW/SCT clouds and <1SM visibility multiple times during the
evening.

The SHSN potential will diminish during the early overnight,
but a final trough passing to the northeast late tonight may
brush the Chicago terminals with SN for a brief 2-3 hour window.
Otherwise, dry conditions are expected for the daytime hours on
Sunday with NW winds gradually diminishing while backing W
through the day.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 3 PM CST Sunday for Winthrop Harbor
     IL to Gary IN.

     Small Craft Advisory until 3 AM CST Sunday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

     Small Craft Advisory from noon Sunday to midnight CST Sunday
     night for Gary to Burns Harbor IN-Burns Harbor to
     Michigan City IN.

     Gale Warning from 3 AM to noon CST Sunday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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